Method of preparing the vinyl chloride based nanocomposite

ABSTRACT

Disclosed are a vinyl chloride based nanocomposite composition and a method of preparing the vinyl chloride based nanocomposite. According to the present invention, a method of preparing a straight vinyl chloride based nanocomposite having a nanomaterial uniformly dispersed therein, by using the vinyl chloride based nanocomposite composition when a vinyl chloride monomer is suspension polymerized in the presence of a protective colloidal agent and a polymerization initiator after preparing a water dispersion suspension using the vinyl chloride based nanocomposite composition based on a hydrophilic composition is provided.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a Divisional application of U.S. patent applicationSer. No. 14/436,720, filed on Apr. 17, 2015, now allowed, which is aNational Stage Entry of International Application No. PCT/KR2014/008615,filed on Sep. 16, 2014, which claims priority to and the benefit ofKorean Patent Application No. 10-2013-0111875, filed on Sep. 17, 2013and Korean Patent Application No. 10-2014-0118563, filed on Sep. 5,2014, all of which are hereby incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a method of preparing the vinylchloride based nanocomposite. More particularly, the present inventionrelates a method of preparing a straight vinyl chloride basednanocomposite having a nanomaterial uniformly dispersed therein, byincluding the vinyl chloride based nanocomposite composition when avinyl chloride monomer is suspension polymerized in the presence of aprotective colloidal agent and a polymerization initiator afterpreparing a water dispersion suspension using the vinyl chloride basednanocomposite composition based on a hydrophilic composition isprovided.

BACKGROUND ART

Vinyl chloride based polymers are used in a variety of fields since theyare cheap and have excellent quality balance.

Vinyl chloride based polymers are largely classified into paste resinsand straight resins.

Paste resins are prepared through emulsion polymerization. Inparticular, monomers, water, a surfactant, and the like are homogenizedusing a homogenization device, and then moved to a polymerization devicefor polymerization. The polymerized paste resins are used in wallpaper,linoleum, and the like.

Straight resins are prepared through suspension polymerization. Thestraight resins are classified into soft and hard products according touse thereof. General soft products are used in wire clothing, wrapfilms, sheets, and the like using large amounts of plasticizer. The hardproducts are used in a variety of fields such as pipes, films, windowframes, and the like by adding a variety of additives such as impactmodifiers, thermal stabilizers, processing aids, pigments, inorganicfiller, and the like.

Vinyl chloride based polymers exhibit weak thermal resistance, impactresistance, and mechanical strength. To supplement the problems, thermalstabilizers, impact modifiers, and inorganic materials are addedthereto. As the inorganic materials, a variety of materials such ascalcium carbonate, silica, titanium oxide, clay, carbon black, zincoxide, and the like are used depending on required properties. Recently,technology to prepare and use nanoscale composites is being developed.

The nanoscale composites (hereinafter, nanocomposites) are composed oftwo or more structure or material types, and mean materials havingnanoscale phase sizes (10⁻⁹ m). In particular, a polymer nanocompositehas mechanical strength such as thermal resistance, impact resistance,and the like dramatically improved by exfoliating and dispersinginorganic nanomaterials of 1 nm to 500 nm over a polymer material. Inaddition, the polymer nanocomposite may have flexibility andmachinability, which are properties of the polymer, and mechanicalstrength, thermal resistance, and the like, which are properties ofinorganic nanomaterials, at the same time, and as such, receives greatattention.

The nanocomposites may satisfy required properties when inorganicnanomaterials are uniformly dispersed in polymer materials. However, inthe case of the vinyl chloride based polymers, it is extremely difficultto prepare nanocomposites by uniformly dispersing inorganicnanomaterials. Accordingly, in most cases, a method of preparing thevinyl chloride based inorganic composites is limited to a method ofmechanically mixing general inorganic materials.

DISCLOSURE Technical Problem

Therefore, the present invention has been made in view of the aboveproblems, and it is one object of the present invention to provide astraight vinyl chloride based nanocomposite so as to improve waterdispersion effects of inorganic nanomaterial by using a vinyl chloridebased nanocomposite composition composed of hydrophilic ingredients, asa basis, and uniformly disperse a hydrophilic inorganic nanomaterialusing the inorganic nanomaterial in vinyl chloride based suspensionpolymerization.

It is another object of the present invention to provide a vinylchloride based nanocomposite composition including a hydrophilicinorganic nanomaterial; and at least one hydrophilic polymer selectedfrom the group consisting of an unsaturated organic acid based polymerand a polycarboxylic acid based (co)polymer.

It is yet another object of the present invention to provide a method ofpreparing the vinyl chloride based nanocomposite by suspensionpolymerizing the vinyl chloride based nanocomposite composition.

Technical Solution

In accordance with one aspect of the present invention, provided is avinyl chloride based nanocomposite composition including a hydrophilicinorganic nanomaterial; and at least one hydrophilic polymer selectedfrom the group consisting of an unsaturated organic acid based polymerand polycarboxylic acid based (co)polymer.

In accordance with another aspect of the present invention, provided isa method of preparing the vinyl chloride based nanocomposite, the methodincluding mixing a hydrophilic inorganic nanomaterial; at least onehydrophilic polymer selected from the group consisting of an unsaturatedorganic acid based polymer and a polycarboxylic acid based (co)polymer;and water, to prepare a water dispersion suspension; adding a protectivecolloidal agent and a vinyl chloride based monomer to the waterdispersion suspension and mixing to prepare a solution; and adding aninitiator to the solution and performing suspension polymerization.

In accordance with yet another aspect of the present invention, providedis a straight vinyl chloride based nanocomposite prepared according tothe preparation method.

Advantageous Effects

As apparent from the fore-going, the present invention advantageouslyprovides a method of preparing a straight vinyl chloride basednanocomposite having a nanomaterial uniformly dispersed therein, byincluding the vinyl chloride based nanocomposite composition when avinyl chloride monomer is suspension polymerized under a protectivecolloidal agent and a polymerization initiator after preparing a waterdispersion suspension using the vinyl chloride based nanocompositecomposition based on a hydrophilic composition is provided.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates surface (×100) and sectional (×3000) scanningelectron microscope (SEM) images of vinyl chloride basedorganic/inorganic nanocomposite particles including nano-silica;

FIG. 2 illustrates surface (×100) and sectional (×3000) scanningelectron microscope (SEM) images of vinyl chloride basedorganic/inorganic nanocomposite particles including nano-clay;

FIG. 3 illustrates surface (×100) and sectional (×3000) scanningelectron microscope (SEM) images of vinyl chloride basedorganic/inorganic nanocomposite particles including nano-calciumcarbonate;

FIG. 4 illustrates surface (×100) and sectional (×3000) scanningelectron microscope (SEM) images of vinyl chloride basedorganic/inorganic nanocomposite particles including nano-titanium oxide;

FIG. 5 illustrates surface (×100) and sectional (×3000) scanningelectron microscope (SEM) images of vinyl chloride basedorganic/inorganic nanocomposite particles including nano-carbon black;

FIG. 6 illustrates an SEM image (×150) of vinyl chloride basedorganic/inorganic nanocomposite particles obtained using a general andsimple dispersant according to Comparative Example 1; and

FIG. 7 illustrates a comparison graph for thermal stability of a vinylchloride based resin, which does not include a hydrophilic inorganicnanomaterial and a hydrophilic polymer, according to Comparative Example2 and a vinyl chloride based nanocomposite according to Example 5.

BEST MODE

Hereinafter, the present invention will be described in detail.

A vinyl chloride based nanocomposite composition according to thepresent invention includes a hydrophilic inorganic nanomaterial and atleast one hydrophilic polymer selected from the group consisting of anunsaturated organic acid based polymer and a polycarboxylic acid based(co)polymer. The vinyl chloride based nanocomposite composition hasimproved hydrophilic inorganic nanomaterial water dispersion effectsand, as such, exhibits excellent impact strength, machinability, andthermal resistance.

In the present invention, the expression “hydrophilic inorganicnanomaterial” means a hydrophilic inorganic nanomaterial used withoutadditional treatment and an inorganic nanomaterial which islipophilically treated. In one embodiment, the hydrophilic inorganicnanomaterial may be at least one selected from the group consisting ofcalcium carbonate, silica, titanium oxide, clay, and carbon black and anaverage diameter thereof may be 1 to 300 nm, 10 to 200 nm, or 20 to 120nm. Within this range, the hydrophilic inorganic nanomaterial mayexhibit excellent impact strength, machinability, and thermalresistance.

In the present invention, the expression “hydrophilic polymer” means atleast one selected from the group consisting of unsaturated organic acidbased polymers and polycarboxylic acid based (co)polymers which are usedwithout additional treatment, so long as not differently specified.

In one embodiment, the unsaturated organic acid based polymer and atleast one selected from the group consisting of polycarboxylic acidbased (co)polymers are included in an amount of 0.1 to 15 parts byweight, 1 to 10 parts by weight, 3 to 10 parts by weight, or 3.3 to 10parts by weight, based on 100 parts by weight of the hydrophilicinorganic nanomaterial. Within this range, the amount of the unsaturatedorganic acid polymer or polycarboxylic acid based (co)polymer remainingin the vinyl chloride based nanocomposite is reduced and dispersioneffects of the hydrophilic inorganic nanomaterial are improved. As aresult, the hydrophilic inorganic nanomaterial exhibits improvedwhiteness or transparency.

The unsaturated organic acid polymer, for example, may be at least oneselected from the group consisting of acrylic acid polymers, methacrylicacid polymers, itaconic acid polymers, fumaric acid polymers, maleicacid polymers, succinic acid polymers, oleic acid polymers, and gelatin.

The polycarboxylic acid based (co)polymer may be a homopolymer or acopolymer including Formula 1 below as a backbone:

wherein each of R₁, R₂, and R₃ is hydrogen or a C1 to C5 alkyl group, M₁is hydrogen, alkali metal, alkali earth metal, a C1 to C10 alkylammoniumgroup, or a C1 to C10 alkyl alcohol ammonium group, and _(m1) is aninteger of 0 to 2.

In addition, in M₁, the alkali metal, for example, is sodium orpotassium, the alkali earth metal, for example, is magnesium or calcium,and the C1 to C10 alkylammonium group is, for example, dimethylammonium,methyl ethyl ammonium, diethylammonium, trimethylammonium,trimethylammonium, or tetramethylammonium. In this case, waterdispersion effects are improved and superior property balance isexhibited.

The C1 to C10 alkyl alcohol ammonium group, for example, may betriethanolammonium or diisopropylammonium. In this case, waterdispersion effects are improved and superior property balance isexhibited.

The polycarboxylic acid based (co)polymer may, for example, be apolymer, which is not identical to the unsaturated organic acid polymer,including at least one selected from the group consisting of carboxylicacid, acrylic acid, methacrylic acid, methyl(meth)acrylic acid,ethyl(meth)acrylic acid, trimethylacrylic acid, maleic acid, fumaricacid, itaconic acid, crotonic acid, citraconic acid, vinyl acetate,4-pentanoic acid, and salts thereof for polymerization.

In addition, a weight average molecular weight of the polycarboxylicacid based resin may, for example, be 10,000 to 100,000 g/mol, or 30,000to 70,000 g/mol. Within this range, dispersion effects of thehydrophilic inorganic nanomaterial and compatibility with a vinylchloride based monomer are excellent.

In addition, the method of preparing the vinyl chloride basednanocomposite using the vinyl chloride based nanocomposite composition,for example, includes mixing the hydrophilic inorganic nanomaterial, atleast one hydrophilic polymer selected from an unsaturated organic acidbased polymer and a polycarboxylic acid based (co)polymer, and water toprepare a water dispersion suspension; adding a protection colloidalagent and a vinyl chloride based monomer to the water dispersionsuspension and mixing to prepare a solution; and adding an initiator tothe solution and suspension polymerizing.

The water dispersion suspension, for example, may include 1 to 20 partsby weight or 4 to 12 parts by weight of the hydrophilic inorganicnanomaterial, based on 100 parts by weight of water. Within this range,property balance is excellent and water dispersion effects of thehydrophilic inorganic nanomaterial are improved during suspensionpolymerization. As a result, properties of the vinyl chloride basednanocomposite are improved.

The water dispersion suspension, for example, may include at least onehydrophilic polymer selected from an unsaturated organic acid basedpolymer and a polycarboxylic acid based (co)polymer in an amount of 0.01to 1.5 parts by weight or 0.1 to 0.5 parts by weight, based on 100 partsby weight of water. Within this range, property balance is excellent andsuperior water dispersion effects of the hydrophilic inorganicnanomaterial are exhibited.

The water dispersion suspension is used in suspension polymerization ofthe vinyl chloride based monomer and, as such, the straight vinylchloride based nanocomposite may be prepared.

The stirring in steps to prepare the water dispersion suspension, forexample, may be carried out for 0.1 to 3 hours or 0.5 to 1.5 hours.

The solution, for example, includes a water dispersion suspension 100 to200 parts by weight and protective colloidal agent 0.001 to 5 parts byweight based on 100 parts by weight of the vinyl chloride based monomer.

The protective colloidal agent, for example, is used in an amount of0.001 to 5 parts by weight or 0.01 to 2 parts by weight. Within thisrange, protective colloidal properties are satisfactory and formation ofmicroparticles or coarse particles is reduced. As a result, particleformation is stabilized.

The protective colloidal agent, for example, may be at least oneselected from the group consisting of a vinyl alcohol based resin, ahydration degree of which is 70 to 98% and viscosity of a 4% aqueoussolution of which is 5 to 100 cps at room temperature, cellulose, andunsaturated organic acid, the cellulose and unsaturated organic acidincluding 15 to 40 wt % of a methoxy group and 3 to 20 wt % of ahydroxypropyl group, and 2% aqueous solutions of the cellulose andunsaturated organic acid having viscosity of 10 to 20,000 cps at roomtemperature. As a specific embodiment, the protective colloidal agentmay be a vinyl alcohol based resin having a hydration degree of 70 to98%, a vinyl alcohol based resin having a hydration degree of 35 to 60%,or a mixture thereof. As another embodiment, the protective colloidalagent may be a vinyl alcohol based resin having a hydration degree of 85to 98%, a vinyl alcohol based resin having a hydration degree of 50 to60%, or a mixture thereof.

In one embodiment, the initiator may be included in an amount of 0.0001to 0.5 parts by weight, or 0.001 to 0.1 parts by weight, based on 100parts by weight of the vinyl chloride based monomer.

The initiator, for example, may be at least one selected from the groupconsisting of diacyl peroxides, peroxydicarbonates, peroxyesters, azocompounds, and sulfates.

The vinyl chloride based monomer may be a vinyl chloride based monomeror a mixture, which includes the vinyl chloride based monomer,polymerizable with the vinyl chloride based monomer. In the case of themixture, the amount of the vinyl chloride based monomer is preferably 50wt % or more.

The vinyl based monomer copolymerizable with the vinyl chloride basedmonomer may, for example, be an olefin compound such as ethylene,propylene, or the like; a vinyl ester such as vinyl acetate, propionicacid vinyl, or the like; a unsaturated nitrile such as acrylonitrile orthe like; or a vinyl alkyl ether such as vinyl methyl ether, vinyl ethylether, or the like. At least one selected from the compounds may be usedas a mix with the vinyl chloride based monomer.

The suspension polymerization, for example, may be terminated by addinga reaction terminator. A resultant slurry may be dried through a generaldrying method. Reaction termination may be carried out when pressure ofa reactor is 6.0 to 8.0 kg/cm², namely, when a polymerization transitionrate is 80 to 90% or 83 to 88%.

The reaction terminator may be any one generally used in preparation ofthe vinyl chloride based resin. For example, the reaction terminator maybe a phenolic compound, amine compound, nitrile compound, or sulfurcompound.

The phenolic compound, for example, may betriethyleneglycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate,hydroquinone, p-methoxy phenol, t-butylhydroxyanisole,n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate,2,5-di-t-butylhydroquinone, 4,4-butylidenebis(3-methyl-6-t-butylphenol), t-butyl catechol, 4,4-thiobis(6-t-butyl-m-cresol), ortocopherol. The amine compound may, for example, beN,N-diphenyl-p-phenylenediamine or 4,4-bis(dimethylbenzyl)diphenylamine.The nitrile compound, for example, may be 2-phenyl nitronyl nitroxide,3-imidazolinenitroxide, or4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl. The sulfur compound,for example, may be dodecyl mercaptan or 1,2-diphenyl-2-thiol. At leastone selected from the compounds may be used.

Additionally, a polymerization regulator, a chain-transfer agent, a pHadjuster, an antioxidant, a cross-linking agent, an antistatic agent, ascale inhibitor, a surfactant, or the like may be partitionally orcontinuously added before polymerization initiation, afterpolymerization, or during polymerization.

The method of preparing the vinyl chloride based nanocomposite throughsuspension polymerization of the present invention, for example, may bea method of preparing the vinyl chloride based nanocomposite bypreparing a hydrophilic inorganic nanomaterial water dispersionsuspension including an unsaturated organic acid or a polycarboxylicacid based polymer and by suspension polymerizing the vinyl chloridebased monomer while maintaining polymerization base temperatureaccording to a target average polymerization temperature during anoverall reaction process in the presence of a protective colloidal agentand a polymerization initiator.

The polymerization base temperature is determined according to a targetaverage polymerization degree and a range of the polymerization basetemperature is 30 to 80° C.

Since the polymerization base temperature depends on characteristics offacility or manufactures, it is difficult to individually selectconditions in all cases for a target average polymerization degree. Forexample, the polymerization base temperature is 63 to 65° C. when thetarget average polymerization degree is 800, polymerization basetemperature is 60 to 62° C. when the target average polymerizationdegree is 900, polymerization base temperature is 56 to 58° C. when thetarget average polymerization degree is 1000, polymerization basetemperature is 52 to 54° C. when the target average polymerizationdegree is 1300, and polymerization base temperature is 47 to 49° C. whenthe target average polymerization degree is 1700. In addition, whenpolymerization base temperature is less than 30° C. or greater than 80°C., a target average polymerization degree may be less than 700 orgreater than 1700.

In addition, a polymerization degree of the vinyl chloride basednanocomposite may be varied according to polymerization temperature and,for example, may be 680 to 2500, or 680 to 1100.

The reactor used in the present invention may be a stirring devicegenerally used to suspension polymerize vinyl chloride based resins. Forexample, as the stirring device, a stirring device, a wing of which is apaddle type, a pitched paddle type, bloomers gin type, a Pfaudler type,a turbine type, a propeller type, or a combination thereof, may be used.As a baffle type, a plate type, a cylindrical type, a D type, a looptype, or a finger type may be used.

Water of a slurry of the vinyl chloride based nanocomposite is removedusing a fluidized bed dryer under general reaction conditions, toprepare the vinyl chloride based nanocomposite.

In addition, a vinyl chloride based nanocomposite prepared by the methodof preparing the vinyl chloride based nanocomposite is provided. Thevinyl chloride based nanocomposite is characterized by uniformlyincluding a hydrophilic inorganic nanomaterial. For example, a contentratio of coarse particles having an average diameter of 100 nm or moreto fine particles having an average diameter of 5 nm or less in thehydrophilic inorganic nanomaterial, for example, is within a range of95:5 to 99:1. Within this range, excellent property balance may beexhibited.

Now, the present invention will be described in more detail withreference to the following examples. These examples are provided onlyfor illustration of the present invention and should not be construed aslimiting the scope and spirit of the present invention.

Example 1

390 kg of deionized water, 1.5 kg of a poly maleic acid vinyl acetatecopolymer as a polycarboxylic acid based (co)polymer, and 30 kg ofnano-silica having a size of 80 nm, were added to a reactor having aninner space of 1 m³ and equipped with a reflux condenser, and thenstirred for 1 hour, to prepare a water dispersion suspension.

With the resultant water dispersion suspension, polyvinylalcohol havinga hydration degree of 87.5% was added in an amount of 150 g andhydroxypropylmethyl cellulose was added in an amount of 150 g to thereactor. Subsequently, 300 kg of a vinyl chloride monomer was addedthereto and then stirred for 1 hour, to prepare a solution.Subsequently, 30 g of di-2-ethylhexylperoxydicarbonate and 120 g oft-butylperoxy neodecanoate were added thereto and then suspensionpolymerization was initiated.

To achieve a target average polymerization degree 1000 during an overallpolymerization process, reaction was carried out while maintaining 57°C. In addition, when a polymerization reactor pressure reached 6.0kg/cm², 15 g of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl and 60 goftriethyleneglycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionateas reaction terminators were added to the reactor and then unreactedmonomers were collected. A resin slurry was collected from thepolymerization reactor.

The obtained slurry was dried in a fluidized bed dryer through a generalmethod. As a result, a vinyl chloride based nanocomposite was obtained.

4 parts by weight of a tin based stabilizer, 1 parts by weight of aprocessing aid (product name: PA-910), 6 parts by weight of an impactmodifier (product name: MB872), and 0.5 parts by weight of a lubricant(product name: SL63) were mixed with 100 parts by weight of the vinylchloride based nanocomposite and kneaded for 3 minutes at 185° C. usinga roll, to obtain a sheet. The resultant sheet was cut, laminated, andmanufactured into a pressed sheet through press forming. Transparency ofthe pressed sheet was measured. As a result, the transparency was 78.8.

Example 2

Polymerization was carried out under the same conditions as in Example1, except that 30 kg of nano-clay having a size of 120 nm was usedinstead of the nano-silica having a size of 80 nm and 1.0 kg ofpolyfumaric acid was used instead of 1.5 kg of the polycarboxylic acidbased (co)polymer as an unsaturated organic acid polymer.

5 parts by weight of a composite stabilizer (product name: WPS-60)including a thermal stabilizer and a lubricant, 1.5 parts by weight of aprocessing aid (product name: PA-828), and 2 parts by weight of titaniumoxide were added to 100 parts by weight of the obtained vinyl chloridebased nanocomposite and calendered for 5 minutes at 185° C. using a rollmill. Subsequently, the resultant product was pressed for 2 minutes at185° C. under a pressure of 10 K/G using a presser, resulting inpreparation of a hard sample. Tensile strength of the obtained samplewas measured based on ASTM D638.

As a result, tensile strength of the obtained sample was 650 kg/cm² andtransparency thereof, which was measured in the same manner as inExample 1, was 77.2.

Example 3

Polymerization was carried out in the same manner as in Example 1,except that 20 kg of nano-calcium carbonate having a size of 40 nm wasused instead of nano-silica having a size of 80 nm, the reaction wascarried out while maintaining temperature to 65° C. to accomplish anaverage polymerization degree of 800 instead of a reaction temperatureof 57° C. to accomplish an average polymerization degree 1000 during anoverall polymerization process, and reaction terminators were added whenpressure of the polymerization reactor reached to 8.0 kg/cm² instead of6.0 kg/cm².

To 100 parts by weight of the obtained vinyl chloride basednanocomposite, 5 parts by weight of a composite stabilizer (productname: WPS-60) including a thermal stabilizer and a lubricant, 1.5 partsby weight of a processing aid (product name: PA-828), and 2 parts byweight of titanium oxide were added, resulting in preparation of amixture. 55 g of the resultant mixture was added at a rate of 40 rpm at180° C. using a Brabender mixer to measure a fusion time. As a result,the fusion time was 105 seconds.

In addition, 5 parts by weight of a composite stabilizer (product name:WPS-60) including a thermal stabilizer and a lubricant, 1.5 parts byweight of a processing aid (product name: PA-828), and 2 parts by weightof titanium oxide were added to 100 parts by weight of the vinylchloride based nanocomposite and then calendered for 5 minutes at 185°C. using a roll mill. Subsequently, the resultant product was pressedfor 2 minutes at 185° C. under a pressure of 10 K/G using a presser,resulting in preparation of a hard sample. Impact strength of the hardsample was measured according to ASTM D256. As a result, the impactstrength of the hard sample was 90 Kgf·cm/cm².

Example 4

Polymerization was carried out in the same manner as in Example 1,except that 15 kg of nano-titanium oxide having a size of 20 nm was usedinstead of nano-silica having a size of 80 nm, the reaction was carriedout while maintaining 65° C. to accomplish an average polymerizationdegree of 800 instead of 57° C. to accomplish an average polymerizationdegree of 1000 during an overall polymerization process, and reactionterminators were added when pressure of a polymerization reactor reached8.0 kg/cm² instead of 6.0 kg/cm².

1.5 parts by weight of a tin based stabilizer and 45 parts by weight ofa plasticizer (DOC) were mixed with 100 parts by weight of the obtainedvinyl chloride based nanocomposite and kneaded for 5 minutes at 150° C.using a roll, resulting in preparation of a sheet. Using a colorimeter,an L value and a b value of the sheets were measured and then awhiteness index (WI) was calculated using the formula below. As aresult, the whiteness index (WI) was determined to be 76.2.

WI=L(L−5.7×b)/100−4

Example 5

Polymerization was carried out in the same manner as in Example 1,except that 10 kg of nano-carbon black having a size of 40 nm was usedinstead of nano-silica having a size of 80 nm, 1.0 kg of a poly maleicacid vinyl acetate copolymer was used instead of 1.5 kg of thepolycarboxylic acid based (co)polymer as an unsaturated organic acidpolymer, the reaction was carried out while maintaining 65° C. toaccomplish an average polymerization degree of 800 instead of 57° C. toaccomplish an average polymerization degree of 1000 during an overallpolymerization process, and reaction terminators were added whenpressure of the polymerization reactor reached 8.0 kg/cm² instead of 6.0kg/cm².

Thermal stability of the obtained vinyl chloride based nanocomposite wasmeasured using a TGA Q50. Results are illustrated in FIG. 7.

For reference, thermal stability measurement conditions are as follows:

<Measurement Conditions>

1: Equilibrate at 40.00° C.

2: Ramp 10.00° C./min to 100.00° C.

3: Isothermal for 60.00 min (removal of remaining H₂O)

4: Ramp 5.00° C./min to 600.00° C.

5: Isothermal for 10.00 min

A surface SEM image and sectional SEM image of each of the vinylchloride based nanocomposites prepared according to Examples 1 to 5 areillustrated in FIGS. 1 to 5.

From the images, it can be confirmed that the vinyl chloride basednanocomposites, in which a content ratio of coarse particles to fineparticles uniformly dispersed by the suspension polymerization is 95:5to 99:1, including the inorganic nanomaterial were prepared.

Comparative Example 1

Polymerization was carried out under the same conditions as in Example1, except that 15 kg of nano-calcium carbonate having a size of 80 nmwas used instead of the nano-silica having a size of 80 nm and 1.5 kg oflauryl phosphate was used instead of 1.5 kg of the polycarboxylic acidbased (co)polymer.

As shown in an SEM image of FIG. 6, a large amount of lump type scaleswere generated due to poor dispersion of the inorganic nanomaterial andthe polymerization process also was not properly performed.

In addition, measurement of the properties of the nanocomposite obtainedaccording to Comparative Example 1 was attempted, according to themethods used in Examples 1 to 5. However, it was impossible to measurethe properties since the hydrophilic inorganic nanomaterial, which doesnot include a hydrophilic polymer of an unsaturated organic acid basedresin or a polycarboxylic acid based resin, was not easily dispersedand, thus, lump type particles were generated, and, accordingly, meltingwas not performed and processing was difficult.

Comparative Example 2

To a reactor having an inner space of 1 m³ and equipped with a refluxcondenser, 390 kg of deionized water was added. In addition, 150 g ofpolyvinylalcohol having a hydration degree of 78%, 120 g ofpolyvinylalcohol having a hydration degree of 40%, and 30 g ofhydroxypropylmethyl cellulose was added to the reactor at the same time.Subsequently, 300 kg of vinyl chloride monomer was added to the reactorand then 30 g of di-2-ethylhexylperoxydicarbonate and 120 g oft-butylperoxy neodecanoate were added thereto. Subsequently, reactionwas carried out while maintaining a polymerization temperature of 57° C.during an overall polymerization process to accomplish an averagepolymerization degree of 1000.

When a pressure of the polymerization reactor reached 6.0 kg/cm², 15 gof 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl and 60 g oftriethylene glycol-bis-3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionateas reaction terminators were added to the reactor. Subsequently,unreacted monomers were collected and a resin slurry was collected fromthe polymerization reactor. The obtained slurry was dried in a fluidizedbed dryer through a general method. As a result, a chloroethylene basedpolymer was obtained.

Properties of the vinyl chloride based resin obtained according toComparative Example 2 were measured in the same manners as in Examples 1to 5. As a result, transparency was 73.1, tensile strength was 525Kg/cm², a melting time was 165 seconds, impact strength was 3.2Kgf·cm/cm², and a whiteness index (WI) was 70.5.

In addition, thermal stability was measured in the same manner as inExample 5 and is illustrated in FIG. 7. As shown in FIG. 7, the thermalstability was dramatically improved by 20° C. or more.

As a result, the examples including the hydrophilic inorganicnanomaterial and the hydrophilic polymer exhibit a transparency of 78.8,a tensile strength of 650 Kg/cm², an impact strength of 90 Kgf·cm/cm²,and a thermal resistance of 76.2. Accordingly, it can be confirmed thatthe examples have improved properties, when compared with the vinylchloride based resin not including the hydrophilic inorganicnanomaterial and the hydrophilic polymer according to ComparativeExample 2.

The examples exhibited improved thermal stability when compared withComparative Example 2 and a melting time of the examples wasdramatically shortened to 105 seconds, when compared with ComparativeExample 2 having a melting time of 165 seconds.

What is claimed is:
 1. A method of preparing a vinyl chloride basednanocomposite hydrophilic inorganic nanomaterial, the method comprising:mixing a hydrophilic inorganic nanomaterial, at least one hydrophilicpolymer selected from an unsaturated organic acid based polymer and apolycarboxylic acid based (co)polymer, and water to prepare a waterdispersion suspension; adding a protective colloidal agent and a vinylchloride based monomer to the water dispersion suspension and mixing toprepare a solution; and adding an initiator to the solution andsuspension polymerizing.
 2. The method according to claim 1, wherein thewater dispersion suspension comprises 1 to 20 parts by weight of thehydrophilic inorganic nanomaterial and 0.01 to 1.5 parts by weight ofthe at least one hydrophilic polymer selected from the unsaturatedorganic acid based polymer and the polycarboxylic acid based(co)polymer, based on 100 parts by weight of water.
 3. The methodaccording to claim 1, wherein the solution comprises 100 to 200 parts byweight of the water dispersion suspension, and 0.001 to 5 parts byweight of the protective colloidal agent, based on 100 parts by weightof the vinyl chloride based monomer.
 4. The method according to claim 3,wherein the protective colloidal agent is at least one selected from avinyl alcohol based resin having a hydration degree of 70 to 98% and avinyl alcohol based resin having a hydration degree of 35 to 60%.
 5. Themethod according to claim 1, wherein the initiator is added in an amountof 0.0001 to 0.5 parts by weight, based on 100 parts by weight of thevinyl chloride based monomer.
 6. The method according to claim 5,wherein the initiator is at least one selected from the group consistingof diacyl peroxides, peroxydicarbonates, peroxyesters, azo compounds,and sulfates.
 7. The method according to claim 1, further comprisingadding reaction terminators when reaction pressure in the suspensionpolymerization reaches 6.0 to 8.0 kg/cm² and drying a slurry in afluidized bed dryer.